1. Field of the Disclosure
The present disclosure relates to input devices, and more particularly to an input device with good noise immunity and good operability.
2. Description of the Related Art
In the related art, there is a capacitive input device that determines an operation position by sensing a variation in capacitance along with input operation.
An operator can intuitively perform an input operation on a capacitive input device in contrast to an input device that has certain operation units such as a switch and a rotary encoder and that is to be operated in a certain manner. Therefore, such a capacitive input device has been applied to various devices and is being used in increasingly diverse environments.
Japanese Unexamined Patent Application Publication No. 2011-100215 discloses an input device having a configuration in which an operation position is calculated by defining a region in which a variation in capacitance along with operation is large and performing a weighted average calculation.
An input device described in Japanese Unexamined Patent Application Publication No. 2011-100215 will be described below with reference to FIGS. 12 to 14 thereof. FIG. 12 is a diagram illustrating the configuration of an input device 900 of the related art. FIG. 13 is an operation timing chart of the input device 900 of the related art. FIG. 14 is a diagram illustrating the states of a region extraction process and a weighted average calculation performed by the input device 900 of the related art.
As illustrated in FIG. 12, the input device 900 described in Japanese Unexamined Patent Application Publication No. 2011-100215 includes a detection panel 911 configured to be operated by an object to be detected such as a finger of a person or a pen, a drive means 921 configured to drive electrodes 913 of the detection panel 911, a current measuring means 931 configured to measure electric charges or current from detection electrodes 914 of the detection panel 911, an insulating means 912 configured to be interposed between the drive electrodes 913 and the detection electrodes 914, a coordinate calculating means 951 configured to determine a position of an object that is to be detected by performing a calculation using the value of the current that is measured by the current measuring means 931, and a control means 971 configured to manage the overall state of the input device 900 and the overall process.
The drive means 921 charges and discharges capacitances that are generated at intersection points of the drive electrodes 913 and the detection electrodes 914 by varying the voltage of each of the drive electrodes 913. The current measuring means 931 measures the capacitances, which are generated at the intersection points of the drive electrodes 913 and the detection electrodes 914, by measuring charging and discharging currents of the capacitances, which are generated at the intersection points of the drive electrodes 913 and the detection electrodes 914.
As illustrated in FIG. 13, in the case where driving of a plurality of cycles and current measurement are performed when capacitances are measured, it is necessary to accumulate a plurality of measurements in order to reduce the influence of noise.
In the region extraction process, values in a region that is pressed by a finger or pen are extracted from values that correspond to the capacitances at the intersection points of the drive electrodes 913 and the detection electrodes 914, and an indication position is calculated by performing a weighted average calculation.
FIG. 14 illustrates the state of the region extraction process and the weighted average calculation. In FIG. 14, vertical lines represent coordinates of the drive electrodes 913, and horizontal lines represent coordinates of the detection electrodes 914. The sizes of black dots at intersection points correspond to the values of the capacitances at the corresponding intersection points. In each of the areas that are surrounded by dotted lines, a group of the intersection points that are adjacent to each other and at which the capacitances having a value larger than a predetermined value are generated, and each of the groups corresponds to, for example, a variation range in the capacitances due to one indicator such as one finger. X marks represent positions that are calculated as indication coordinates by a weighted average calculation.
However, although an accumulation process has been performed as a measure of noise in the above-described related art, it is necessary to increase the number of accumulations in order to improve the noise removal effect in the accumulation process, and thus, the processing speed is reduced. As a result, there have been problems in that the followability with respect to an input operation is impaired, and the operability deteriorates.
In addition, since a weighted average calculation is simply performed on only the values within the region, which have been extracted, there have been problems in that the coordinates of an operation position may be falsely calculated, and a malfunction such as a false detection may occur in the case where noise is not completely removed through the accumulation process.
These and other drawbacks exist.